Interchangeability of CSF and PET to identify Alzheimer's disease pathology

INTRODUCTION Establishing interchangeability between cerebrospinal fluid (CSF) and positron emission tomography (PET) for patient identification may improve access to Alzheimer's disease (AD) therapies. METHODS Alzheimer's Disease Neuroimaging Initiative participants with mild cognitive impairment or AD dementia and available CSF, florbetapir PET, and/or flortaucipir PET were included. The interchangeability of CSF (per label threshold/method) and PET was evaluated for patient identification. RESULTS Fujirebio Lumipulse amyloid beta (Aβ) 42/Aβ40 ( N = 288) and Roche Elecsys phosphorylated tau 181 (P‐tau181)/Aβ42 ( N = 251) Conformité Européene (CE)‐marked CSF assays were in high agreement with and non‐inferior to florbetapir PET for identifying patients with AD pathology. High agreement was observed between Roche Elecsys CSF P‐tau181/Aβ42 ( N = 127) and an early (temporal) flortaucipir PET stratification. DISCUSSION CSF assays were interchangeable with amyloid PET to identify patients with AD pathology and were in high agreement with elevated early temporal flortaucipir PET. CSF biomarkers may be used as a robust alternative to PET, potentially increasing access to AD diagnosis and disease‐modifying treatments.